What is swatting? It's basically someone calling the 911 service, spoofing the callerid and pretending to be under attack from some maniac. What happens then is that a SWAT team is sent to the residence on which the spoofed phone number is registered. Obviously the end result is the SWAT team end up harassing the family / residents living there on behalf of the person who spoofed the call in the first place.

Quite a nasty joke if you ask me - and VoIP caller-id spoofing makes it very easy to pull off.